Electrical conductor.



.No.'789,651.' I PATENTED MAY 9, 1905. o. L. BURLINGHAM & w. J. BURTON.

ELECTRICAL CONDUCTOR.

APPLICATION FILED FEB. 16. 1903.

* Lzitlfoz'l 08,06.

No. 789,651. I Patented May 9, 1905.

UNITED STATES PATENT OFFICE.

CHARLES L. BURLINGHAM AND WILLIAM. J. BURTON, OF CHICAGO, ILLI- NOIS,ASSIGNORS, BY MESNE ASSIGNMENTS, TO SAID BURTON AND JUANITA M.BURLINGHAM.

ELECTRICAL CONDUCTOR.

SPECIFICATION forming part of Letters Patent No. 789,651, dated May 9,1905.

Application filed February 16,1903. Serial No. 143,509.

T 107107711 it y 200271: of greater resistance than the interior copperBe it known that we, CHARLES L. BURLING- conductor unbalances thecircuit. HAM and WILLIAM J. BURTON, citizens of the The primary ob ectof our invention Is to United States, residing at Chicago, county ofprovide a flexible electrical connector which 5 Cook, State-of Illinois,have invented a cerwill avoid the objections above pointed out tain newand useful Improvement in Electrical and which will possess therequisite conduc- Connectors; and we declare the following to be tivityand at the same time be resilient and a full, clear, and exactdescription of the indurable. vention, such as will enable othersskilled in A further object of our invention is to pro- 10 the art towhich it pertains to makeand use vide a flexible electrical cordcomprising a the same, reference being had to the accomplurality ofinsulated conductors so arranged panying drawing, which forms a part ofthis as to render the cord thoroughly flexible and specification. at thesame time of small diameter.

Our invention relates generally to electrical A still further object ofour invention is to 15 connectors, and more particularly to flexibleprovide a flexible connector which Wlll be cordssuch, for instance, asare used for coneflicient and durable in use. necting subscribers at atelephone switch Our invention generally described consists board. in anelectricial cord comprising one or more It is essential that flexibleelectrical conspirally-disposed conductors, each consisting 20 nectorswhich are subjected to frequent use in acentral wire possessingstructural strength in completing circuits should possess the reqandresiliency surrounded by a material pos uisite electrical conductivityand at the same sessing high electrical conductivity. time besufliciently strong and resilient struc- Our invention further consistsin an elec- 7 turally to stand constant bending without trical connectorcomprising a plurality of in- 5 breaking or destroying the conductivity.sulated conductors coiled in a single spiral.

Owing to the lack of resiliency and strength Our invention will be morefully described of copper, considerable difliculty has beenexhereinafter with reference to the accompanyperienced heretofore inconstructing flexible ing drawing, in which the same is illustratedconnectorssuch, for instance, as switch as embodied in a convenient andpractical 3 board-cordswhich will stand constant usage form.

without wearing out or short-circuiting in a The figure in the drawingillustrates a cord comparatively short while, especially whenconstructed in accordance with our invention the diameter of theconnector is necessarily and united to a plug. of limited size. Aconductor commonly used I/Ve have shown the cord as comprising two .35in making switchboard-cords is composed of a conductors; but it isevident that one or more number of strands of tinsel-that is, a fibrousthan two of such conductors may be wound thread and a filament of coppertwisted tospirally together to constitute the cord. Each gether. Theconstant flexure of tinsel, howconductor consists in a wire A, of ametal pos- 5 ever, soon breaks the filaments of copper and sessingstrength and resiliencysuch, for in- 4 results in a short circuit whenthe cord constance, as brass, aluminium, or steel. In sists in more thanone conductor. It has practice a steel wire, such as is commonly beenproposed to avoid the objection to tinsel known as a piano-wire, hasbeen found by constructing cords of an interior conductor preferable.

i of copper and an exterior surrounding con- B indicates a fine copperwire, which is 45 ductor of a metal possessing greater strength woundaround the wire A to impart to the and resiliency; but such cords areopen to the conductor the necessary electrical conducobjection that theexterior conductor being tivity.

G designates an insulating-covering around each conductor, which mayconveniently consist in silk wound around the same.

D indicates a covering for retaining the silk insulation in place aroundeach conductor and may conveniently consist in braided thread.

The conductors are wound together in the form of a spiral the diameterof which is approximately that of the thickness desired for the cord.The spiral is surrounded by an outer covering E, which may convenientlyconsist in braided cotton thread. A second covering F, surrounding thefirst covering E, is also preferably provided,which is composed ofbraided linen thread.

When the connector is to be used as a switch board-cord, its oppositeends are secured within a plug Gr, comprising conducting portions G andG insulated from each other and to which the ends of the conductors areseparately connected.

It is evident that by winding a plurality of conductors which are toconstitute a cord in the-form of a spiral a number of conductors may beemployed without increasing the diameter of the cord. It is also evidentthat by arranging the conductors in the form of a spiral the cord isrendered thoroughly flexible and capable of continued usage Withoutbreaking or short-circuiting. Byconstructing each conductor of aninterior wire possessing structural strength and resiliency and of asurrounding material possessing high electrical conductivity a conductorresults which possesses the requisite conductivity and at the same timepossesses sufiicient structural strength to render the cord durable andcapable of hard usage without breaking or short-circuiting.

\Vhile we have described more or less precisely the details ofconstruction, we do not wish to be understood as limiting ourselvesthereto, as we contemplate the changes in form, the proportion of parts,and the substitution of equivalents as circumstances may suggest orrender expedient without departing from the spirit of our invention.

Having now fully described our invention, what we claim as new, anddesire to secure by Letters Patent, is

1. A switchboard-cord consisting of a flexible conductor wound inparallel convolutions and composed of a strong resilient wire aroundwhich is wound a copper wire.

2. In a switchboard-cord, the combination with a plug, of a spiralflexible conductor connected to the plug and composed of a strongresilient wire surrounded by a good conducting material.

3. In a switchboard-cord, the combination with a plug, of a plurality ofinsulated conductors wound in parallel convolutions to form a singlecontinuous spiral, each conductor being composed of a strong resilientwire around which is wound a copper wire.

In testimony whereof we sign this specification in the presence of twowitnesses.

CHARLES L. BURLINGHAM. WVILLIAM J. BURTON.

WVitnesses:

E. H. BELL, GEO. L. TILKINSON.

